The ability of nanoparticles to carry large drug payloads and the ease with which ligands can be added so that the payload is delivered to specific target sites (e.g. cancer or cardiovascular disease) make them particularly promising for biomedical applications. The chemical composition and physical properties of nanomaterials such as shape and elasticity can significantly impact their fates in vivo. Recent studies indicate that filamentous nanomaterials have superior pharmacokinetic and tumor-homing properties. Decuzzi et al., Journal of Controlled Release 141, 320-327 (2010).
Several viral nanoparticles (VNPs) are currently being developed for nanomedical applications, where the vast majority of platforms under investigation are of spherical nature, e.g. the Human papilloma virus (HPV)-based Gardasil vaccine, Adenovirus-based gene-delivery vectors, and various plant viruses including Cowpea mosaic virus (CPMV), Brome mosaic virus (BMV), Cowpea chlorotic mottle virus (CCMV), Hibiscus chlorotic ringspot virus (HCSRV), and Red clover necrotic mottle virus (RCNMV). In contrast, few high aspect ratio VNPs have been investigated. Those that have, including Tobacco mosaic virus and bacteriophage M13, have focused mainly on in vitro tissue engineering applications. Pokorski, J. K. and N. F. Steinmetz. Mol Pharm 8(1): 29-43 (2011).
Still, the vast majority of platform technologies currently under development consist of spherical or elongated low aspect ratio materials (AR<5). While carbon-based nanotubes and filomicelles are notable exceptions, carbon nanotubes have low biocompatibility (Firme et al., Nanomedicine: nanotechnology, biology, and medicine 6, 245-256 (2010)) and filomicelles are in the micron-size regime. Geng et al., Nat Nanotechnol 2, 249-255 (2007). Physically and chemically tailoring materials at the nanoscale in two dimensions to create high aspect ratio materials is challenging using synthetic materials, mainly due to polydispersity and poorly controlled chemistry. Efforts in synthetic chemistry and nanotechnology have sought to mimic characteristics such as self-assembly and programmability at the atomic level that nature has already achieved. Therefore, a bio-inspired approach to engineer viral nanoparticles (VNPs) from plants for imaging and drug delivery is desirable.